Section 2

Covalent Bonding

Covalent Bonds

Covalent bonds form

When atoms share electrons to complete octets.

Between two nonmetal atoms.

Between nonmetal atoms from Groups 4A(14), 5A(15), 6A(16), and 7A(17).

Hydrogen Molecule (H2)

In a hydrogen molecule (H2), each H atom

Shares electrons to form a covalent single bond.

Acquires two (2) electrons.

Becomes stable like helium (He).

Forming Octets in Molecules

In a fluorine F2 molecule, each F atom

Shares one electron. Acquires an octet.

Diatomic Elements

These elements share electrons to form diatomic, covalent molecules.

Learning Check

What is the name of each of the following diatomic molecules?

H2 ______________________

N2 _______________

Cl2 _______________

O2 _______________

I2 _______________

Carbon forms 4 covalent bonds

In a CH4, methane, molecule

The central C atom shares 4 electrons to attain an octet.

Each H atom shares 1 electron with the carbon atom to become stable like He.

Electron-Dot Formula for NH3

In NH3, a N atom is bonded to three H atoms. N and 3 H

The electron dot structure is written as: H Bonding pairs H

│ H : N : H or H─N─N

lone pair of electrons

Electron-Dot Formulas and Models of Some Covalent

Compounds

Single and Multiple Bonds

In a single bond One pair of electrons is shared.

In a double bond, Two pairs of electrons are shared.

In a triple bond. Three pairs of electrons are shared.

Electron-Dot Formula of CS2

Write the electron-dot formula for CS2.

STEP 1 Determine the atom arrangement. The C atom is the central atom.

S C S

STEP 2 Determine the total number of valence

electrons for 1C and 2S.

1C(4e-) + 2S(6e-) = 16e-

Electron-Dot Formula of CS2

STEP 3 Attach each S atom to the central C atom using one electron pair.

S : C : S

16e- - 4 e- = 12e- left

STEP 4 Attach 12 remaining electrons as 6 lone pairs to complete octets.

.. .. : S : C : S : .. ..

Electron-Dot Formula of CS2

STEP 5 To complete octets, form one or more multiple bonds.

Convert two lone pairs to bonding pairs between C and S atoms to make two double bonds.

.. .. .. .. : S : : C : : S : or : S = C = S :

A Nitrogen Molecule has A Triple Bond

In a nitrogen molecule, N2,

Each N atom shares 3 electrons. Each N atom attains an octet. The sharing of 3 sets of electrons is a multiple

bond called a triple bond.

Covalent Compounds

• Weak forces between molecules, not the strong covalent bonds within each molecule, are responsible for the physical properties of covalent compounds.

• Covalent compounds have relatively low melting and boiling points.

• Most covalent compounds are poor electrical conductors.

• Strong forces within molecules, weak forces between them

Strong covalent bonding forces within molecules

Weak intermolecular forces between molecules

Polar Covalent

• Polar covalent is a description of a bond that has an uneven distribution of charge due to an unequal sharing of bonding electrons.

The boy is not equally sharing with anyone else but rather taking all the food for himself.

+ +

-

-

-

Polar Covalent

Non-Polar Covalent

• Non polar covalent is a covalent bond that has an even distribution of charge due to an equal sharing of bonding electrons.

This couple is non- polar because they are sharing the drink equally between them.

Non-Polar Covalent

Just as a summary to what each bond looks like…